Morphometric cadaveric assessment of suprascapular and axillary nerve trajectories in relation to glenohumeral landmarks relevant to reverse total shoulder arthroplasty.

Abstract

Background: Reverse total shoulder arthroplasty (RTSA) is increasingly used for complex shoulder pathology but carries a risk of iatrogenic nerve injury, particularly to the suprascapular (SSN) and axillary nerves (AXN). Detailed morphometric data on their relationship to glenoid landmarks remain limited.

Methods: Forty embalmed adult cadavers (60 shoulders) were dissected at PGIMER, Chandigarh, after ethics approval (PGI/IEC/2024/EIC000563). The SSN and AXN were exposed, and distances from nerves to glenoid "clock-face" positions and to osseous landmarks were measured with digital calipers. Data were analyzed for sex- and side-based variations using appropriate parametric or non-parametric tests and descriptive statistics.

Results: The SSN was 27-34 mm from the 12 o'clock glenoid in 75% of shoulders, with males showing significantly greater distances than females (p < 0.001). At the posterior 9 o'clock (or 3 o'clock) rim, the SSN lay 16-20 mm away, more closely in females. The AXN was within 1-4 mm of the inferior capsule in 40% and in direct contact in 22%, with no significant sex- or side-based differences. The SSN bifurcation and its vertical relation to the humeral neck showed consistent patterns.

Conclusion: Reproducible morphometric patterns of the SSN and AXN relative to glenoid landmarks were identified. Female shoulders demonstrated closer SSN proximity, highlighting sex-related anatomical variability relevant to RTSA. These findings emphasize the importance of individualized surgical planning and may inform assessment of anatomical safety margins for implant placement. Further clinical studies are required to validate their clinical significance.